1. Field of the Invention
The present invention is generally related to a wireless pH measurement system, and more particularly to a wireless pH measurement system fabricated by semiconductor processes.
2. Description of the Prior Art
With the advance in economics, the standard of living becomes higher and the life style and diet are also drastically changing. Thus, modern people become over-nourishment to have many chronic diseases, such as hypertension, diabetes, gout, heart disease. Therefore, household medical equipments will be important equipments for every family. Before measuring the pH value in blood, it should be understood that the pH value in blood is important to human body and how diet affects human body.
The acidity or basicity of food does not depend on taste but is the result from digesting food and metabolizing by human body. After metabolism, if the food generates more ions, like phosphate ion, sulfate ion, chloric ion, it forms acids in human body to generate acidic reaction. If the food generate more ions, like sodium ion, potassium ion, magnesium ion, calcium ion, it forms base in human body to generate basic reaction. It is also related to the mineral content in the food. Generally, those including more sulfur and/or phosphor mineral matters belong to acidic food while those including more potassium, magnesium, calcium mineral matters belong to basic food.
Food intake is preferably controlled to be acid-base balance. Although the acidity or basicity of food only has very tiny influence to human body, nutrition is unbalanced if intake is too acidic or basic and health will be affected after a long period of time. Human body has a good acid-base buffer system to maintain body fluid at a constant pH value, about in the range of pH7.35˜pH7.4. However, it is still important to have balanced food intake.
The so-called acidic food means that the food generates more anions, such as phosphate ion (PO43−), sulfate ion (SO42−), chloric ion (Cl−), than cations, such as sodium ion (Na+), potassium ion (K+), magnesium ion (Mg2+), calcium ion (Ca2+) and thus these excess amount of anions form acid to generate acid reaction. On the contrary, it is basic food if generating more cations than anions. Therefore, those including more sulfur and/or phosphor mineral matters belong to acidic food while those including more potassium, magnesium, calcium mineral matters belong to basic food.
A pH sensor can use an ion sensitive field effect transistor as its electrode, the sensing principle of which is described as follows. The ion sensitive electrode is placed in an unknown solution. The total amount of ions diffusing to the interface electric double layer changes along with the concentration of the ions in the unknown solution. The ions diffusing to the electric double layer are electrically attracted by ion selective substances so as to combine to each other. While the tested ions approach the voltage type sensing electrode, the electrode has voltage induction so as to generate an electric potential signal because ion itself has either positive charge or negative charge.
Ion sensitive field effect transistors have the advantages of miniaturizability and mass production, low cost, high input impedance and low output impedance, fast response, compatibility with MOSFET processes. In addition, many related papers have been reported [Jia Yong-Long, “Study of the extended gate field effect transistor (EGFET) and signal processing IC using the CMOS technology”, June, 2001, Department of electrical engineering, Chung Yuan Christian University, Ph. D. dissertation, pp. 1-12 and 85-97; Chen Jia-Chi, “Study of the disposable urea sensor and the pre-amplifier”, June, 2002, Department of biomedical engineering, Chung Yuan Christian University, Master dissertation, pp.32-40; Liao Han-chou, “Novel calibration and compensation technique of circuit for biosensors”, Master dissertation, Department of electrical engineering, Chung Yuan Christian University, pp. 11-27, June, 2004; Chen Jheng-cheng, “study of using tin dioxide film to fabricate array type pH sensing device”, June, 2003, Department of electrical engineering, Chung Yuan Christian University, Master dissertation, pp.47-65; Liao Hung-Kwei, “Application of tin oxide sensing film on ion selective field effect transistors, June 1998, Department of electrical engineering, Yuan Christian University, Ph. D. dissertation, pp. 23-42].
At present, wireless transmission technique and application has not been used in the pH measurement. Therefore, the present invention provides a convenient wireless pH measurement system to achieve the measurement of physiologic parameters and the design of real time environmental monitoring system.